In recent years, a field-effect transistor (hereinafter referred to as FET) using an organic semiconductor excellent in moldability as a semiconductor layer has been proposed. Since by utilizing an organic semiconductor as an ink, it becomes possible to form a circuit pattern directly on a substrate, by inkjet technique or screening technique, FET using the organic semiconductor is being studied actively in place of the conventional inorganic semiconductor.
As an important index showing performance of FET, mobility is exemplified. Improvement in mobility means improvement in switching property of FET. For example, in a liquid crystal display apparatus, it leads to realization of high gradation. In the case of the liquid crystal display apparatus, mobility of FET is required to be 0.1 cm2/V·sec or more.
In addition, as another important index, there is hysteresis. Hysteresis expresses a variation wide of a current value relative to voltage history, and it is necessary to make a value of hysteresis small for stably driving FET.
As a technique for improving mobility, a method of using a polymer composite having a carbon nanotube composite, in which a conjugated polymer is attached to a part of the surface of a carbon nanotube (e.g. see Patent Literatures 1 to 3), is disclosed. However, when a semiconductor layer formed of the polymer composite containing a carbon nanotube composite is used, although mobility is improved, there was a problem that hysteresis is great.